Chapter 16
IN THIS CHAPTER
Looking into the field of toxicology
Analyzing toxins
Applying test results to forensic problems
Understanding common drugs and poisons
During the millennia since Socrates drank the hemlock that killed him, lethal use of poisons has waned a bit, in part because scientists now know how to trace poisons to those who use them for nefarious purposes. From taking arsenic to overdosing on heroin to drinking too much water (I kid you not), poisoning deaths nowadays are the realm of the toxicologist, who has become a critical component of today’s crime labs. Drugs and poisons of all types often are involved in harmful accidents and accidental, suicidal, and homicidal deaths, and they may even be contributory factors in many natural deaths.
Have you ever taken a poison? I bet your answer is, “Of course not!” But you’re wrong. You take poisons every day. In fact, you have to take poisons to live. Don’t believe me? Try not to drink any water. Try not to breathe.
You see, anything can be a poison. The basic definition of a poison is any substance that, when taken in sufficient quantities, causes a harmful or deadly reaction. So a poison basically is a substance that either harms you or kills you. But, the key here is the phrase “sufficient quantities.” The degree of toxicity of any substance depends on how much enters your body and over what period of time it does so. For example, you probably already know that arsenic is a poison, but did you know that you probably have arsenic in your body right now? If you’re a smoker, you have more than a little bit. Your body also has some mercury and cyanide inside. These substances are in the environment, and you can’t avoid them. But they’re in such small quantities that they cause no real harm. Take enough of any of them, however, and you’re a goner.
I know, I know, you believe the cyanide and arsenic deals, but what’s this about water and air?
Even substances that cure can poison. Digitalis, for example, is an extremely common cardiac medication derived from the foxglove plant, but it’s also a deadly poison. Too much can lead to nausea, vomiting, and death from dangerous changes in the rhythm of the heart. How ironic that it can treat some abnormal heart rhythms but also can cause other, more deadly rhythms. It’s all in the dose. The right dose is medication; the wrong dose is poison.
Toxicology is a marriage of chemistry and physiology and deals with drugs, poisons, and other toxic substances, and how these substances alter or harm living organisms, particularly humans. Although toxicology is a relatively new science, the first toxicological test dates back to 1775, when Swedish chemist Karl Wilhelm Scheele discovered a way to prove that arsenic was the culprit in a suspicious death.
Today, the forensic toxicologist’s job is to find a toxin and determine its likely effect on the individual who ingested or otherwise came in contact with it. For example, the forensic toxicologist may
On the other hand, not finding a drug may be just as important. Suppose, for example, that the toxicologist finds no drugs in someone who’s exhibiting erratic or bizarre behavior. Such a situation may lead to a psychiatric evaluation and ultimately to a diagnosis and appropriate treatment. Similarly, the toxicologist may find that the level of a seizure medication in the blood was too low for the driver of a vehicle involved in an accident, and may conclude that a seizure was the cause of the accident.
Most poisons don’t cause visible changes in the body — neither in a living person nor during an autopsy. Some do, but most poisons work their mischief within the cells of the body and leave behind no visible footprints. As a result, the medical examiner (ME) doesn’t often see visible evidence of toxins on the corpse or on the microscopic slides of any body tissues obtained as part of the autopsy. Therefore, the ME collects fluids and additional tissues from the body that the toxicologist analyzes for the presence or absence of toxins.
Metallic elements also cause disease and death. Excess iron, mercury, lead, arsenic, antimony, selenium, and many other metals can lead to serious health problems and can even kill you. These metals have caused accidental, suicidal, and homicidal deaths for many years.
Part of poison’s popularity is that it’s sneaky. Toxins rarely leave behind visible clues, so finding a toxin, and enough evidence to determine that it was the cause of death, is a tricky business that involves several specialized tests and a variety of bodily tissues and fluids.
Urine: Easily sampled with a cup and a trip to the restroom, urine testing is a staple of workplace drug testing. It can also prove useful during an autopsy. Because kidneys are situated along one of the body’s major drug and toxin elimination routes, toxicologists can often find such substances in greater concentrations in the urine than in the blood. However, the correlation between urine concentration of a drug and its effects in the body is poor, at best. The urine level can reveal that the drug had been in the blood at some earlier time, but it can’t determine whether the drug was exerting any effect on the individual at the time it was collected.
Likewise, toxicologists can’t estimate blood concentrations from urine concentrations. The concentration of any drug in the urine depends on how much urine the individual produced. If someone drank a great deal of water, the urine and any chemicals it contains become more diluted than they are for someone who hasn’t consumed large quantities of water.
The medical examiner ultimately is responsible for determining the cause and manner of death, and toxicological findings can play an important role in making those determinations. Unfortunately, toxicological findings rarely provide a black-and-white, clear-cut answer, because drugs and poisons may be the cause or merely a contributing factor in any cause or manner of death.
A person may die of natural causes, but drugs may be involved in the mechanism of death. If someone with significant coronary artery disease (CAD), for example, takes an amphetamine or cocaine, that person’s heart rate and blood pressure increase, his clogged arteries can’t accommodate the demand, and a heart attack can follow. The cause of death would be a heart attack, but the amphetamine or cocaine would be a contributory factor.
When the ME and the toxicologist confront this situation, they must assess the extent of the victim’s heart disease, the amount of the drug in the body, and whether a heart attack actually occurred. If the amount of drug is low and the victim had severely diseased coronary arteries, they may conclude that the death was natural and that the drug was only a minor contributing factor. On the other hand, if his CAD was mild but the level of the drug in his body was high, the death likely was accidental, and the drug was the mechanism.
Most accidental poisonings occur at home and often involve children. Curious by nature, children eat or drink just about anything — pesticides and paint thinners included. In adults, accidental poisoning most often occurs because a product is mislabeled, usually because someone placed it in a container other than its original one.
Other major causes of accidental death from poisons or drugs are dose miscalculations or dangerous mixtures of drugs. Addicts often miscalculate the amount of heroin or amphetamine they’re taking and die from this mistake. In addition, people often have unfounded beliefs, for example: “If one dose of a drug is good, then two must be better.” Mixing prescription sedatives and alcohol also is notoriously lethal.
Suicide is the most common manner of death in poisonings. Common agents include, narcotics, sedatives, carbon monoxide, and even prescription drugs. Many suicides involve multiple drugs, and this presents a difficult problem for the toxicologist. Analysis of stomach contents, blood, urine, and tissues taken from internal organs helps determine the levels of each drug and allows the toxicologist to assess how each drug contributed to the victim’s demise. If one particularly toxic drug is present in large amounts, it is likely the cause of death; but if multiple drugs are involved, it becomes more difficult to determine that a given combination of drugs was the cause.
Although homicidal poisonings were common from antiquity to the 20th century, they’re less common today. Guns now seem to be the preferred method. In the remote past, determining why someone died was difficult, and ascertaining whether a poison was involved was virtually impossible. Modern toxicology, however, has changed all that. Nonetheless, determining that poisoning was the cause of death still is one of the most difficult tasks for the forensic toxicologist and pathologist.
As is true of accidental and suicidal poisonings, homicidal poisonings occur most often at home, meaning that the killer usually knows about the victim’s habits and has access to the victim’s food, drink, and medications. Knowing who has this type of knowledge can be critical to the ME and police investigators when probing cases of homicidal poisoning.
Literally thousands of drugs and chemicals are harmful, addictive, or lethal — what a headache for the toxicologist! An understanding of the circumstances surrounding a death is of utmost importance for determining how and why it happened. Clues at the scene often point toward a particular drug or poison. For example, finding a young girl on her bed at home with an empty pill bottle at her side would lead to one avenue of testing, and finding a long-term addict in an alley with fresh needle marks would point to another path. The more clues that the circumstances of the death can supply, the narrower the field of possibilities the toxicologist must consider.
Presumptive tests are used for initial screening and typically are easier and cheaper to perform. When negative, they indicate that the drug or toxin in question isn’t present, and the toxicologist doesn’t need to perform further testing for it. When positive, the results indicate that a particular substance may be present.
In general, these tests are more sensitive but less specific than confirmatory tests. They yield more false-positive results, but are unlikely to give false negatives.
A good confirmatory test is sensitive and specific, recognizes the chemical in question, and can identify it to the exclusion of all others. After a chemical has undergone a screening test and the toxicologist has established a presumptive identity, a confirmatory test can accurately determine the true identity of the unknown substance.
Infrared spectroscopy also determines the chemical fingerprint of the substance being tested but exposes the substance to infrared light instead of electrons. When exposed to infrared light, each compound transmits, absorbs, and reflects the light in its own unique pattern. These unique patterns determine which compounds are present and thus identify the chemical substance being tested.
After testing has revealed the presence and concentration of a chemical substance, the hard part begins. The toxicologist now must assess what the results mean, evaluating each of the drugs present, identifying routes of administration, and determining whether concentrations that are present played a role in the subject’s behavior or death. From such determinations, the toxicologist decides whether a drug could have caused the victim to lose control of a car or exhibit violent or aggressive behavior, for example, and whether a drug caused or contributed to the victim’s death.
In general, the concentration of the drug or poison is greatest at the site where it’s administered. For example:
Finding a large amount of a toxin in the victim’s stomach doesn’t necessarily mean that the drug was the cause of death; it may not yet have been absorbed into the blood and distributed to the body. Thus, the level of the drug in the blood is more important than the concentration of the drug in the stomach contents. The toxicologist must see evidence that the drug was absorbed before he can attribute harm or death to the drug.
After determining a blood level of a certain chemical, the toxicologist assigns the level one of these four broad categories:
In general, the concentration of a drug or its metabolites in urine doesn’t reliably indicate the effects of the drug on the subject. The physiological effects of the drug depend upon its concentrations within the blood and various tissues of the body, including the brain. Many drugs and their metabolites are concentrated in the urine in preparation for elimination from the body, which means the concentration may be falsely high. A time lag exists between when the drug is at maximum concentration in the blood and thus has its maximum effect on the individual, and when it appears in and concentrates in the urine. Simply put, the elimination process takes time, so the urine concentration lags behind the blood concentration.
At times, toxicologists are called upon to determine whether a poisoning is acute (quick but intense) or chronic (drawn out in small doses). A good example is arsenic poisoning. Arsenic can kill when it’s given in a single large dose or when it’s given in repeated small doses during the course of weeks or months. In either case, the blood level may be high. But determining whether the poisoning was acute or chronic may be extremely important. The suspect list for an acute poisoning may be long, but the suspect list for a chronic poisoning would include only those who had long-term contact with the victim. A family member, a caretaker, or a family cook would qualify.
Every little bit helps when trying to get to the bottom of a possible poisoning, and the ME and the toxicologist use any and all evidence, including the results of toxicological testing, the autopsy examination, and statements from investigating officers and witnesses. To use this information, they must
Although a discussion of every known chemical, drug, and poison wouldn’t fit in this book, I provide a peek at many of the poisons, toxins, legal and illegal drugs, and chemicals that the ME and the toxicologist are likely to encounter.
Ethanol, or drinking alcohol, is by far the most commonly abused drug. Its toxic effects are potentially lethal, and the loss of coordination and poor judgment associated with its use can lead to violent and negligent acts. Alcohol is physically addictive, and withdrawal can be an arduous and dangerous process. Without proper medical treatment for alcohol addiction, death rates from withdrawal syndromes such as delirium tremens (DTs) can be 20 percent or more.
Blood-alcohol concentration (BAC) correlates very well with the degree of intoxication. The level is expressed in grams percent, or the number of grams of alcohol in every 100 milliliters of blood. As the BAC level rises, the toxic effects of the alcohol become more pronounced. A level of 0.08 percent is the legal limit for intoxication in most jurisdictions. You may become impaired at a much lower level, but at 0.08 percent, they’ll cuff you.
A police officer who detains you as a suspect for driving under the influence (DUI) goes through several steps to determine whether you are, indeed, intoxicated. The first is a field sobriety test, in which the officer asks you to stand on one foot, stand steady with your eyes closed, repeatedly touch one finger to your nose, or walk a straight line in the heel-to-toe manner. These are done to determine how the alcohol you’ve consumed is affecting the coordination and balance centers of your brain. Alcohol makes performing each of these tasks clumsy or even impossible. Contrary to what many think, you can’t fake a field sobriety test. Physiology conspires against you, and you end up stumbling, wavering, or poking yourself in the eye.
The officer may also ask you to take a breath test (see the sidebar “Exhaling the evidence: Breathalyzer tests”). If so, you’re probably cooked. Alcohol passes unchanged through the lungs, going directly from the bloodstream into the air sacs of the lungs and out with each breath, so you can’t fake a breath test, either. The alcohol content in your lungs directly correlates with your blood-alcohol level. The higher the level in your blood, the higher the concentration in your exhaled breath. A breath test, therefore, is extremely accurate.
If you fail a field sobriety test or a breath test, a blood-alcohol concentration (BAC) test may be performed to determine the exact level, particularly if you’ve been involved in an accident or caused property damage, bodily harm, or the death of another. Most hospitals and crime labs can accurately and rapidly determine your BACs. The preferred testing method is gas chromatography (see the earlier section “Presuming the results”).
In suspected alcohol-caused deaths, the ME measures the alcohol level in cadaver blood to determine whether the intoxication level is high enough to have caused or contributed to the death. However, the blood-alcohol level in some corpses actually increases because of the action of bacteria, some of which produce alcohol. To get around this problem, the ME makes a determination of the alcohol level in the vitreous humor of the eye because it reflects a blood-alcohol level with a one- to two-hour lag. So, the vitreous humor can tell the ME what the blood-alcohol level was one to two hours before death.
Embalming a body may make determining the blood-alcohol level at the time of death difficult, if not impossible. During the embalming process, embalming fluid replaces most of the blood, leaving behind little for testing, in most cases. The embalming fluid also contains alcohol, but it’s methanol and not ethanol (drinking alcohol). Because the alcohol in the embalming material doesn’t enter the vitreous humor after death, the toxicologist can test the vitreous for ethanol. If ethanol turns up in the vitreous humor, it had to have been in the victim’s blood before death.
Opiates, barbiturates, alcohol, and other tranquilizers are central nervous system (CNS) depressants that make you sleepy and lethargic and thus are referred to as downers.
Opiates are chemicals derived from the sap of poppies and are divided into natural, semisynthetic, and synthetic, depending upon their source and method of manufacture. They are narcotic sedatives (sleep producing) and analgesics (pain relieving) that produce euphoria, lethargy, and, in larger doses, coma and death from respiratory depression and asphyxia. You can take most either by mouth or injection; all come with great risk of abuse and physical addiction.
Natural opiates, like morphine and codeine, come directly from the poppy. Heroin actually is diacetylmorphine and is produced by combining morphine with acetic anhydride or acetyl chloride. Heroin is by far the most commonly abused opiate.
In the living, the toxicologist uses the Marquis test to screen samples for the presence of morphine and other opiates. During an autopsy, the ME collects a blood sample for the toxicologist to analyze to determine whether the deceased used heroin.
Autopsy findings in individuals who die from heroin overdoses are fairly consistent. The ME usually finds evidence of pulmonary edema, or water in the lungs; however, that isn’t always the case. Curiously, the lungs often show evidence of talc crystals and cotton fibers because those substances are used respectively to cut and filter the heroin. When the drug is intravenously administered, blood carries these crystals and fibers through the heart, and then they filter from the blood and become trapped by the lungs.
Barbiturates are derived from barbituric acid, and people use them as hypnotics, or sleeping pills. Among the five barbiturates commonly used in the past (pentobarbital, amobarbital, secobarbital, butabarbital, and phenobarbital), only phenobarbital remains in wide use today. Phenobarbital is an excellent anticonvulsive (seizure-preventing) medication used by many individuals afflicted with epilepsy. The others have been replaced with newer and safer hypnotics. Still, these old drugs are available and frequently abused. Because both barbiturates and alcohol can suppress respiration and even cause a cessation of breathing, their combination is particularly dangerous and may lead to coma and death from asphyxia.
A color test is used to screen for the presence of barbiturates in biological tissues (blood, urine, organs).
The most commonly used stimulants, or uppers, are amphetamines and cocaine. They increase alertness, lessen fatigue, and suppress appetite. However, with continued use, they also cause irritability, anxiousness, aggressive behavior, paranoia, fatigue, and depression. These reactions make sense because people who are hopped up all the time tend to eat and sleep poorly, overreact to stress, and simply vibrate through life, which is likely to wear anyone out. Furthermore, when it does, physical fatigue and mental exhaustion set in, which may be why one slang name for certain amphetamines is crank — they make the user unpleasant and cranky.
Amphetamines, such as crystal methamphetamine, are highly addictive, widely abused, and easily manufactured in garage labs. Because abuse of these compounds is common and widespread, testing for amphetamines is part of virtually every hospital and crime lab toxicology screen.
In the bloodstream, cocaine is converted to methylecgonine and benzoylecgonine. Urine tests target the latter of these two compounds and can find traces for up to three days after the last use. Toxicologists use both immunoassay and the Scott Color Test as screening tests for cocaine.
Hallucinogens are trippy. They alter perceptions and mood, lead to delusional thinking, and cause hallucinations. Delusions basically are false beliefs that have little or no basis in reality. Hallucinations are sensory experiences that aren’t real and can affect any or all of the senses; they can be visual (sight), auditory (sound), olfactory (smell), taste, or tactile (touch).
The most frequently encountered hallucinogens come either from the plant world (marijuana, peyote, and mushrooms) or the chemistry laboratory (LSD, STP, and PCP).
By far the most commonly used (and one of the mildest) hallucinogen is marijuana. It goes by many street names including Mary Jane, weed, and pot. It is a cannabinoid, which means it’s derived from the Cannabis sativa plant. The active ingredient, tetrahydrocannabinol (THC), is found in marijuana at a concentration of 2 percent to 6 percent, but higher concentrations are becoming more common. Hashish, the oily extract of the plant, contains approximately 12 percent THC.
Peyote is a small Mexican cactus. Its active ingredient is mescaline, which is a hallucinogen in the alkaloid family. Many native tribes have used it in their tribal ceremonies for centuries. The surface of the cactus is covered with small round bumps called peyote buttons. These buttons are divided into sections like an orange, and each section contains a cotton-like tuft inside. Either TLC or GC can confirm the presence of alkaloids. Further testing to identify mescaline isn’t necessary because possession of the plant material itself is illegal.
Mushrooms present a different problem. The mere possession of marijuana and peyote is illegal, but the possession of mushrooms isn’t. And that means the toxicology lab must identify the psychoactive components (psilocin and psilocybin) of the mushroom before it can be deemed illegal.
A wide variety of chemically-produced hallucinogens are available. The most common ones are lysergic acid diethylamide (LSD) and phencyclidine (PCP, or angel dust). LSD is potent, and as little as 25 micrograms can produce an acid trip that lasts for 12 hours. Although LSD isn’t directly fatal, the hallucinations it produces are typically vivid. Users in many instances have harmed themselves because of these altered perceptions. The primary screening test for LSD is the Van Urk Color Test.
PCP use can lead to aggressive and psychotic behavior. The toxicologist can use either blood or urine for PCP testing. Urine tests may remain positive for a week after the last use.
You’ve no doubt heard of the so-called date-rape drugs or rave drugs. They’ve been the subject of a considerable number of criminal actions and civil litigations. The conviction of Andrew Luster, the heir-apparent to the Max Factor fortune, was based on his illicit use of GHB (gamma-hydroxybutyrate).
The major date-rape drugs are Rohypnol (flunitrazepam), Ecstasy (3,4-methylenedioxymethamphetamine), GHB, and ketamine (ketamine hydrochloride).
These drugs cause sedation, a degree of compliance, poor judgment, and amnesia of events that occur while under their influence. The loss of event memory makes these drugs effective in date-rape situations. A criminal can easily slip a small amount of GHB or Rohypnol into the victim’s drink or a bottle of seemingly innocuous water. The victim may then leave with the would-be assailant because the drug impairs judgment and enhances euphoria. Only later does the victim realize that something happened, but memories of events are spotty or even absent altogether.
Recreational use of any of these drugs is a proverbial crapshoot. The quality and purity are variable, even with the pharmaceutically manufactured Rohypnol and ketamine, because they often are cut (combined with other materials, such as talc) or mixed with other drugs by the time they reach the street. Thus, users know neither what drugs nor exactly what amounts they’re ingesting. And because reactions vary widely from person to person and are unpredictable, you need to make a huge leap of faith to start using these dangerous chemicals — even more frightening when you realize that many people actually use any number of different drugs at the same time. Unfortunately, many young people willingly experiment with them and end up visiting the morgue.
An odd, but not rare, form of substance abuse is the sniffing of volatile chemicals. This practice also is known as huffing. It began with glue and gasoline but has spread to include napthalene (moth balls), toluene (paint thinners, fingernail polish, and some paints), and trichloroethylene (paint thinners and liquid typewriter correction fluid). Other commonly abused gases are gasoline, kerosene, and nitrous oxide (the “laughing gas” used by dentists).
People who inhale the fumes of these volatile chemicals can experience giddiness, euphoria, dizziness, slurred speech, headache, nausea, and vomiting. With continued exposure, loss of consciousness, coma, and death can follow. Permanent damage to the brain, liver, heart, and kidneys also can occur.
Because these gases are volatile, they rapidly break down in the body or are quickly excreted through the lungs. The toxicologist therefore may not be able to find them in the blood or tissues of the user. Often, the toxicologist determines the chronic use of these dangerous chemicals by finding damage to the liver, lungs, and kidneys of the user.
The abuse of anabolic steroids has become epidemic among athletes. These hormones appear naturally in the body in very small amounts, and when taken in large amounts, they cause muscle growth, increased strength, and improved reflexes — exactly what an athlete needs to compete. But steroids are a double-edged sword. They also cause hair loss, impotence, and liver damage (including liver cancer), and can lead to aggressive behavior (called “steroid rage”).
Users typically are easy to recognize as they tend to be big, muscular, and athletic. The screening and confirmatory tests mentioned earlier in this chapter detect most synthetic steroid preparations, but unscrupulous chemists constantly create newer and more difficult to detect “designer” steroids. The forensic toxicologist must continually search for new testing techniques to find these banned drugs in athletes.
Though poisons aren’t used for homicide as often as they once were, the forensic toxicologist is still confronted with cases of accidental, suicidal, and homicidal poisoning.
Cyanide is one of the most lethal chemicals known. It can enter the body by inhalation, ingestion, or through the skin by direct contact. Cyanide gas, or hydrogen cyanide (HCN), is used for executions.
Cyanide is a metabolic poison, which means it damages the internal workings of the cells. During autopsy, the ME may suspect cyanide poisoning from the bright, cherry red color of the victim’s blood.
Strychnine is a plant-based component of some rat and mole poisons. It possesses an extremely bitter taste, which makes it difficult to disguise in food or beverage. Its well-deserved reputation for causing a lot of pain makes it a rare choice for suicides.
Strychnine causes powerful convulsive contractions of all the body’s muscles. The body adopts a posture known as opisthotonos, which means the back is arched, and only the back of the head and the heels of the feet touch the floor. That isn’t pretty. Death results from asphyxia because breathing is impossible during such violent muscular contractions. After death, rigor mortis often occurs quickly because the muscles are depleted of adenosine triphosphate (ATP) during their contractions (see Chapter 11).
Oxalic acid, which you can find in raw rhubarb, can lead to accidental poisonings. Ingestion of this plant causes harm in two basic ways. First, it’s a powerful irritant to the gastrointestinal tract and causes mouth, throat, and esophageal pain and possibly bleeding. However, its major toxic effects come from the chemical properties of the oxalic acid found in its leaves and stalks. When oxalic acid is absorbed into the bloodstream, it reacts with calcium in the blood, forming calcium oxalate, which can cause cardiac arrest and death. The calcium oxalate produced by this chemical reaction is filtered through the kidneys, where it can clog microscopic tubules and severely damage the kidneys. Survivors often require dialysis or even a kidney transplant.
During an autopsy of someone who dies from this plant, the ME finds a burned and irritated mouth, esophagus, and stomach; low blood-calcium levels; and calcium-oxalate sludge in the kidneys.